<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
	  <script>
	    let fd = new FormData();
	    console.log(fd)
	    fd.set("a","a")//会覆盖
	    fd.set("b","b")
	    fd.append("a","a2")//重复
	    console.log(fd.getAll("a"))//拿去所有的a  ["a", "a2"]
	  </script>
	</body>
</html>
